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UNITED STATES PATENT OFFICE.

J OHN WICKS, 0F COLUMBUS, OHIO, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed February 23, 1916.

Z '0 all whom it mciy concern:

Be it known that I, JOHN VVICxs, a citizen of the United States of America, and a resident of Columbus, county of Franklin, and State of Ohio, have invented certain new and useful Improvements in Automatic Telephone Systems, of whicn the following is a specification.

My invention relates to automatic telephone systems and has partictlar reference to methods of handling toll or long distance connections in such systems. In general my invention contemplates the provision of a comprehensive system of automatic calling over serially related long distance lines, the arrangement being such that an operatar at any exchange in the system is enabled to establish connection with subscribers in any other exchange without the intervention of intermediate operators.

I am aware that automatic calling over toll lines is not altogether new but to the best of my present knowledge such calling has heretofore been restricted to lines ex tending between two exchanges only. The system of my invention makes a substantial advance over what is old in the art by providing means whereby an operator at an originating exchange can connect through the medium of automatic switches with subscribers in a second exchange; and can also connect, by means of one of the same switches, with a toll line extending to a third exchange, where the connection may again be extended to local subscribers or to other toll lines.

Since at the intermediate exchanges all the toll lines must be capable of being called as well as of calling, and since they must be arranged for local as well as through connections, in which latter case the impulses and signaling currents have to be re layed, special apparatus must be provided to take care of these different contingencies; and it is the articular object of my invention to provi e for each toll line terminating at an intermediate exchan e such an apparatus, as will appear more c early hereafter.

A further object of my invention is to provide mean included in the above apparatus whereby a distant operator, having operated the intermediate exchange apparatus to select a line to a third exchange, may at her option signal the operator at the third Specification of Letters Patent.

Patented Aug. 26, 1919.

Serial No. 30,042.

exchange manually, or connect automatically with local subscribers at the third exchange.

Further objects of my invention are to incorporate the foregoing into a system in which the lines are phantomed in accordance with well known practice; to provide means for sending regulated operating impulses over simplex circuits superimposed on the physical lines in the above system; and to accomplish all the foregoin without detracting from the talking e ciency of the lines, or interfering with their use for regular manually established connections.

These and other objects will appear more clearly and will be explained more fully in the detailed specification, reference being had to the accompanying drawings.

For a clear understanding of the drawings, Figures 2, 3, 4, 5, 6, 7, and 8 should be arranged in order with their lines at the sides thereof in alinemen't, Fig. 1 should be joined at its right hand end to the left side of Fig. 2, Fig. 9 should be joined at its left hand end to the right side of Fig. 8, Fig. 5' should be joined at the top to the bottom of Fig. 5, and Fig. 10 should be joined at its left hand end to the right side of Fig. 5. The apparatus shown in Figs. 1, 2, and 3 is located in what I shall hereinafter designate as the No. 1 exchange, the apparatus shown in Figs. 4, 5, 6, 5*, and 10 is located in what I shall hereinafter designate as the No. 2 exchange, while the apparatus shown in Figs. 7, 8, and 9 is located in what I shall hereinafter designate as the No. 3 exchange.

When the drawings are properly laid out and joined together it will be seen that I have shown two toll lines, indicated by reference characters 105-106 and 205-206, extending from the No. 1 exchange to the No. 2 exchange, and two other toll lines, indicated by reference characters 305306 and 405406, extending from the No. 2 exchange to the No. 3 exchange. Each toll line is shown connected through a repeating coil with a repeater and a jack at each end. For example, the toll line 105-106 is shown con nected by means of repeating coil R at the No. 1 exchange with the jackJ and the repeater E and by means of repeating coil R at the No. 2 exchange with the jack J 6 and the repeater M. It will be readily seen that each of the other three toll lines is similarly equipped. In addition to the above, each toll line has an extension by way of its associated re eater at the intermediate exchange exten ing to a toll selecthr N, N, etc., and also a second extension leading to multiple contacts in the banks of these toll selectors. It is plain that the toll selectors provide means for establishing through connections over two serially relatedtoll lines.

Apparatus is also provided in connection with the two parallel toll lines 105-106 and 205-206 whereby a phantom circuit is formed extending from jack J 3 in the No. 1 exchange to jack J in the No. 2 exchange. Similarly, a second phantom circuit is superimposed on parallel toll lines 305306 and 405-406 and extends from jack J in the No. 2 exchange to jack J in the N0. 3 exchange. It is to, be understood that the phantom circuits are adapted for use in manually established connections only while the physical circuits may be used both for manually and automatically established conneotions.

To better facilitate the understanding of my invention I have elected to show a part of the apparatus in operated position whereby a com lete circuit connection has been established: between a calling substation A (Fig.1) in the No. 1 exchange, and a called substation A (Fig. 9) inthe No. 3 exchange. The said connection extends from substation A by way of line conductors 11 and 12, conductors 13 and 14, multiple jack J, cord circuit P jack J, repeating coil R toll li-ne 105-106, repeating coil R, repeater M toll Selector N, repeater M repeatin coil R, toll line 305-306, repeating coil R, repeater E and connector H to the line conductors of substation A The substation A (Fig. 1) may be of any suitable type or construction and as shown herein is of the general type disclosed in British patent to T. Gr. Martin, No. 1419 of 1910. It comprises essentially the receiver 2, transmitter 3, switch hook 4, ringer 5 and cond' user 6. Bein an automatm substation it is also provi' ed with a pair of impulse sprinlgs 7 and; 8' controlled by the impulse wh ee 9 throu h the medium of a finger'hole dial (not s-own).

' line eonductorsll' and 12 of the substation A, are connected at the No. 1 exchange to the individual line switch C which may be of the genera type disclosed in British patent to'R. James, No. 26,301 of 1906; bein however, of the particular gype s gwn in United States Letters Patent 0. 1,0 8,690, granted Jan. 17th, 1912, to Frank Newforth. Since line switches of the abovety' e are well known and since they form no pa of my invention an extended description will not e given. It will sufiice to say here that through the medium of line switch C'the ine ofi substation A is iven access to a plurali y of selector swltches (not shown) which may be of the general type disclosed in the British patent to Automatic Telephone Manufacturing ($0., No. 2543' of 1914. A three conductor trunk line which run be extended to one of these solector switches is indicated by reference characters 31, 35, and 36.

For the purpose of controlling a group of line switches such as the line switch G, there is provided a master switch D, which is of the general type disclosed in ltiritish atent to R. W. James, No. 26,301 of 1906; eing, however, more nearly of the particular type disclosed in British patent to T. G. Martin No. 1419 of 1910. The function of the master switch, as is well known, is to maintain all the idle line switches of its associated group in operative relation with an idle trunk line.

In addition to the line switch 0 there is also provided for the line of substation A a multiple jack .1, which, as shown herein, directly accessible to the toll operator. It is to be understood that the toll operator may complete connections locally by any other in own method, however, the method shown having been chosen principally on account of its simplicity.

At P I have shown a toll operators cord circuit which may be of any suitable type. As shown herein, it comprises among other details the battery supply relay 51 which, in connection with sleeve relay 50, controls the supervisory lamp L; and the ring up looking relay 52 which, in connection with the sleeve relay 55, controls the supervisory lamp L Keys K and K are ringing keys and key IQ is a listening key. The talking strands of the cord are connected through condensers 56 and 57.

The toll operator. besides havin access to lines of the local subscribers, has )efore her multiple jacks which are terminals of toll lines extending to other exchanges. I have shown three such 1jacks, J, J, and J ,which jacks are termina s of circuits extending to exchange No. 2. Of these three circuits, the physicals, represented by jacks J and J are equipped tor automatic calling, as will presently be made clear.

The apparatus shown at F (Fig. 3) is, with the exception of the calling device S individual to the toll line 105-406. The calling device 53 may be common to a number of toll lines. or, preferably, there may be one such calling device for each toll operator. The key K" serves to associate the corresponding toll line with the calling device at the proper time. The reference character 76 represents an impnlsing relay of hi gh resistance and having magnetically distinct cores. Reference characters 510, 74,

77, and 7 5 indicate, respectively, an impedance coil, a cut-off relay, a switching relay, and an ordinary drop for receiving signals.

The cut-off relay 74, when actuated, serves to disconnect the connections extending to the repeater E and to the drop 7 5. The switching relay, when actuated, shifts the normal ground connection of the impulsing relay 76 to the ungrounded pole of battery B. A slight inspection of the drawings now will show that each toll line is equipped at its terminus in the No. 1 exchange or No. 3 exchange with apparatus similar to that shown at F'. Or, in other words, the apparatus shown at F (Fig. 3), F (Fig. 7), and F (Fig. 7) is precisely like that shown at I (Fig. 3) which has just been described.

At the No. 2 exchange the toll line 105106 is extended through the medium of repeating coil R to the multiple jack J. The apparatus directly associated with jack J indicated by reference character 0 comprises a cut-off relay 125, a drop 126, and a key K by means of which the corresponding toll line may be associated with the calling device S. The apparatus shown at O, and is precisely like that shown at The repeater M which has been previously referred to, is of utility for setting up automatic connections in either direction over its associated toll line. For handling incoming automatic calls from the No. 1 exchange a four conductor trunk line indicated by reference characters 201, 202, 203, and 204 is provided. This trunk line may be traced through Fig. 5 to Fig. 5 where it ter minates in the toll selector N. Similarly, the repeater M, associated with toll line 205-206 and precisely like repeater M is provided with a trunk line indicated by refercnce character 220, which extends through Fig. 5 to Fig. 5" where it terminates in the toll selector N. The repeaters M and M, associated, respectively, with toll lines 305- 306 and 4054-06, are also precisely like repeater M in construction and function: and are also provided each with a trunk line, which trunk lines are indicated, respectively by reference characters 221 and 207, and which extend through Fig. 5 to Fig. 5 and there terminate, respectively, in toll selectors N and N. More briefly stated, each toll line terminating in the No. 2 or intermediate exchange has access, through its associated repeater M Or M etc, to a toll selector such as N or N, etc. The operation and functions of the various relays of the M type of repeaters will be described fully in the detailed specification. It may be mentioned here, however. that the impulsing relay 112 of repeater M and corresponding relays of the repeaters M, M, and M are similar to relay 76- (Fig. 3) which has already been described.

The toll selector N is'of the general type of selector switch disclosed in U. S. Letters Patent No. 815,321, granted March 31, 1906, to Keith, Erickson and Erickson; being,

however, more nearly of the particular type disclosed in British patent to the Automatic Telephone Manufacturing 00., No. 2M3 of 1914. Among other details, the toll selector N* comprises a bank of contacts arranged in horizontal rows or levels, which contacts are adapted to be engaged by a set of wipers 270, 271, 272, and 273, carried upon a shaft (not shown) which has a vertical movement controlled by the vertical magnet 256, and a rotary movement controlled by the rotary magnet 257. The operation of the various parts of the switch is controlled through the medium of the double wound line relay 250. Means for permitting the switch to be restored to normal position is provided in the release magnet 254 which, upon energizing, withdraws the retaining pawls from the shaft. The contacts 262 and 263 make against their respective springs only when the shaft has been raised one or more steps from its normal position. The relay 260, bridged across the line conductors 265 and 266, is of high resistance and is designed to operate on alternating current. The relays 255, 258, and ringing relay 261 are slow acting, z'. 0., each of these relays is able to retain its armature for an instant after its energizing circuit has been broken.

Considering now the bank contacts of the toll selector N 4 more in detail, it will be seen that I have shown in the drawing (Fig. 5) three of the horizontal levels and two sets of contacts in each level. It is to be understood, however, that there may be more conlarts than shown herein, there being generally provided in actual practice ten of the horizontal levels each with ten sets of contacts. From the first set of contacts of the first level there extends a three conductor trunk line, indicated by characters 212, 213, and 214, which terminates in the connector switch H (Fig. 10). The second set of contacts in the first level is provided likewise with a trunk line 215, which extends to a connector switch (not shown) similar to the connector H. In the same manner each of the other sets of contacts in the first level may be provided with a trunk line extending to a connector switch similar to connector H".

The first set of contacts in the second level is provided with a, trunk line whose conductors are separately numbered 208, 209, 210, and 211, and which extends upward through Fig. 5 and terminates in the repeater M (Fi 6). The second set of contacts in the second evel is provided with a trunk line, indicated by reference character 216, which extends upward through the lower right hand corner of Fig. 5 and terminates in the repeater M (Fig. 6). Since the repeaters M and M are associated, respectively, with the toll lines 305306 and 405406, which extend to the No. 3 exchange, it will be clear that the second level is the level assigned to the toll lines extending between the No. 2 and No. 3 exchanges. In fact were there other such toll lines besides the ones shown they would appear at additional contacts in the second level.

In like manner the first and second sets of contacts in the third level are terminals of trunk lines indicated by reference characters 217 and 218, and which terminate, respectively, in the repeaters M and M (Fig. 4). W hence it follows that the third level is the level assigned to the toll lines extendin between the No. 2 and No. 1 exchanges. ere there additional exchanges and connecting toll lines terminating in the No. 2 exchange, the toll lines extending to each separate additional exchange would be assigned to a separate level in the toll selector bank such as the fourth or fifth level, for example. Further consideration of Fig. 5 will show that each trunk line leading from the con. t acts in the bank of selector N is also multipled to corresponding contacts in the banks of all the remaining toll selectors. From the foregoing considerations the following conclusion may be drawn: The toll lines terminating in the N o. 2 or intermediate excha are provided each with a toll selector switch, which switches have access in common to connectors for completing local connections, and also have access to all of the toLl lines themselves, the connectors and various groups of toll lines being assigned to separate levels in the toll selector banks.

Continuing with the description of the apparatus, it has already been mentioned that the repeater M and apparatus F are similar to corresponding parts in Figs. 4 and 3. AtE (Fig. 8) I have shown a repeater which is of the general type disclosed in U. S. Letters Patent No. 1,136,912, granted April 20, 1915, to Talbot G. Martin, although the circuits are modified somewhat to enable the repeater to operate in conjunction with the apparatus shown at F 3 (Fig. 7). The operatlon and functions of the various relays of the repeater will be described more fully in the detailed specification.

By means of conductors 510 and 511 the repeater E is connected directly with connector H (Fig. 9) which is of the general type of connector disclosed in U. S. Letters Patent No. 815,17 6, granted March 13, 1906, to Keith, Erickson and Erickson; being however. more nearly of the particular type disclosed in the British patent to the Automatic Telephone Mfg. Co., No. 2270 of 1914. Among other detailsthe connector H comprises a bank of contacts arranged in horizontal rows or levels, which contacts are adapted to be engaged by a set of wi ers 530, 531, and 532 carried upon a shaft not shown) which has a vertical movement eontrolled by the vertical magnet 518, and a rotary movement controlled by the rotary magnet 519. The usual side switch comprising the wipers 525, 526, 527, and 528 is controlled by the private magnet in the well known. manner. The operation of the various parts of the switch is controlled by the double wound line relay 512 which relay, in the case of purel local connections, also serves to supply tal ingcurrent to the calling line. The called line is provided with talking current from the windings of the double wound answering bridge relay 515. The ringing relay 524 affords means for projecting ringing current over the called line to signal the called subscriber. Means for restoring the switch to normal position is provide in the release magnet 516 which, upon energizing, withdraws the retaining pawls from the shaft and restores the side switch wipers to their first position. The contacts 536 and 537 make contact with their respective springs only when the shaft has been raised one or more steps from its normal position. The relays 517 and 521 are slow acting.

The connector H has access through its wipers and bank contacts to a group of subscribers stations one of which is shown at The substation A may be similar to substation A (Fig. 1) already described, and is like that substation provided with an individual line switch, shown at C and with multiple jacks, of which one is shown at J. Each of the substations in the No. 3 exchange is of course, similarly provided with a line switch and with multiple jacks, the former being of service in setting up local connections, while the latter enable the toll operator or operators to connect the corresponding substations with toll lines extendin to other exchanges, as for example, the tol lines 305306 and 405-406. For this urpose cord circuits are provided, one of which is shown at P (Fig. 8) this cord circuit being similar to the one shown at P (Fig. 2).

The repeaters E and E (Fig. 2) and E (Fig. 8) are similar to repeater E (Fig. 8) and are each assumed to be connected directly to a connector switch such as connector H (Fig. 9); one of these connectors, the one to which repeater E is connected, being in fact, shown at H (Fig. 1). The connectors to which repeaters E (Fig. 2) and E (Fig. 8) are connected are not shown. The connector H and associated connectors are provided for the purpose of completing connections to the lines of substations terminatin in the No. 1 exchange, one of which, t e one shown at A (Fig. 1), has already been described.

It has been explained how the toll selectors have access through one of their bank levels to connector switches such as the connector H (Fig. 10). The connector H and associated connectors are similar to connector H (Fig. 9) and are provided for the purpose of completing connection with the lines of substations terminating in the No. 2 exchange, one of which substations is shown at A (Fig. 10). The substation A is similar to substation A (F ig. 1) and like that substation is provided with an individual line switch C for use in establishing local automatic connections; and is also rovided with multiple jacks, one of which is shown at J These latter are provided to enable the toll operator or operators to complete connections between a calling (or called) subscriber, the one at substation A, in this case, and a toll line. For this purpose there are provided cord circuits which may be similar to the one shown at P. The cord circuit shown at P is somewhat different from the other cord circuits shown in that it is provided with a ring up and lockin supervisory rela in each end of the cor instead of only 1n the toll end. This cord circuit may be used for manually completing through toll connections.

While I have shown the toll selectors and repeaters E, E etc., as having direct access to the connector switches, it will be evident to those versed in the art that selector switches may be used in the well known manner for increasing the capacity of the system. Selectors which may be used are of the type disclosed in British atent to the Automatic Telephone Mann acturing 00., N0. 2543 of 1914.

The various devices for preventing interference between the two physical circuits and between the physical and phantom circuits form no part of this invention, since they are fully described and claimed in the copending application of Frank Newforth, Serial No. 69633, filed Dec. 31, 1915.

It is thought best however, to describe these devices briefly as follows: Considering the phantom circuit superimposed on toll lines 105-106 and 205-206, the phantom repeating coil R has its line windings joined by a pair of condensers 501 and 502 in series, and in the same manner the re peating coil-R has its line windings joined by the condensers 503--504. These condensers prevent the flow of direct current between the physical circuits. The junction of each of these condenser pairs is connected to the junction of a pair of low resistance high impedance retardation coils, indicated by reference characters 505508, inclusive, which are themselves connected in series with the exchange battery. These coils serve to take u the charging and discharging currents o the condenser pairs, thereby preventing these currents from interfering with the operation of the impulsing relays such as relay 76 (Fig. 3.) To admit of using alternating current on the phantom circuit for signaling without interfering with the operation of the impulsing relays, such as relay 76 (Fig. 3), the retardation coils 510 and 512 (-Fi 3) and 511 and 513 (Fig. 4) are rovide Each of the calling devices C, 5 etc., is provided with a condenser 514, 515, etc., in shunt thereof, which condensers serve to smooth out the sharp breaks when sending impulses and thereby prevent impulses sent over one of the physical circuits being heard on the phantom circuit.

The toll lines 305306 and 405-406 and the phantom circuit superimposed thereon are similarly equipped to prevent interference.

Throughout the drawings I have shown a plurality of batteries but it is to be understood that there is preferably but one battery for each exchange, each battery having its positive terminal grounded. Each exchange also is provided with a busy signaling machine, such as T, T, etc., an interrupter, such as I, I etc; and with a ringing current generator, such as Gem", Gen, etc.

Having given a general description of the apparatus I will now proceed to a more detailed description of the operation of the same. Inasmuch as a great deal of the automatic apparatus shown herein is well known and has been described in the publications previously referred to, the o eration of such apparatus will be describe in a more or less general manner, the details being given only where they have reference in some respect to the application of the principles of my invention. I will first descrlbe how a connection is established between substation A in the No. 1 exchange and substation A in the No. 3 exchange, this being the complete connection shown in the drawings and previously referred to. The call is assumed to have originated with the subscriber at substation A and the complete connection 1s, therefore, handled by the operator at the N0. 1 exchange. Afterward certain other connections will be briefly described with a view to demonstrating the great flexibility of the system.

Referring now to Fig. 1, the subscr ber at substation A, in initiating a long distance call, must first t in communication with a so called recor ing operator at the No. 1 exchange. Any approved method of accomplishing this object will serve, but since the substation A is an automatic substation, it will be assumed that the subscriber has called the operator automatically as follows: Upon removing the receiver at substatlon A, the line switch 0 is operated to extend the line conductors 11 and 12 through to a. selector switch, which may be the selector to which the trunk conductors 34, 35, and 36 extend. After the line switch. has operated, the subscribcr may manipulate the finger hole dial of his instrument, thereby operatin the selector switch to select a group 0 trunks cxtciid'iiig to recording operators positions; after which the selector operates automatirally to connect with an idle one of these trunks, all in a well known manner. The calling subscriber, upon hearing the operator respond, will give her the necessary infor mation, such as the name and address of the person with whom conversation is desired, and also his own name and telephone numher; and will then replace his receiver, thereby restoring the line switch and selector switch to normal position. The recording operator in the meantime has Written out the data received from the subscriber on a ticket, which is passed to a toll operator whose duty it is to complete the required connection.

In the case under consideration the wanted subscriber is located in the No. 3 exchange which must be reached via the No. 2 ex change. The toll operator, therefore, after first testing the toll line 105-10G with the tip of her plug in the regular manner to determine its idle or busy condition, inserts the calling plug of cord circuit P in the jack J of toll line 105-106, it being assumed that this toll line was not in use. By the insertion of the plug in the jack a circuit is completed as follows: ground at G (Fig. 3), winding of relay 74, conductor 73, contact s rings 63 and 64 of relay 60, conductor 94, s eeve of jack J sleeve of plug inserted therein, and winding of sleeve relay 55 to battery B. Relay 55 upon energizing prepares a circuit for the supervisory lain) L and also disconnects the test wire 58 from the tip side of the cord. Relay 74, upon an ergizing, separates contact springs 88, 89, and 90 and contact springs 91, 92, and 93, thereby disconnecting the conductors 71 and from the dro 75 and from the line relays 61 and 62 o the repeater E Relay 74 also prepares a circuit for relay 77 by closing} contact springs 86 and 87.

he operator may now throw the key K associated with the toll line 105-406, thereby completing an initial energizing circuit for relay 77 as follows: ground at G, contact springs 86 and 87, contact springs and 91, and winding of relay 77 to battery B. The actuation of key K also inserts the calling device S in a circuit which will be mentioned later. Relay 77, upon energizing, short circuits the contact s rings 85 and 94 of the key K by means 0 contact springs 604 and 605; and shifts contact spring 602 from its normal restin place against cont-act spring 601 to its war ing position against contact sprin 603 thereby completing a circuit including the im ulsing relays 76 (F", Fig. 3) and 112 (M 4) as follows: ground at G (Fig. 4:), contact springs 159 and 160, contact springs 165, 166, and 167,

winding of relay 112, winding of retardation coil 511, windings 107 and 108 of repeating coil It in parallel, line conductors 105 and 106 in parallel, windings 103 and 104 in parallel, winding of retardation coil 510 winding of relay 76, contart springs 002 and 603, contact springs 78 and 80, impulse springs 81 and 82 of calling device S, and resistance 95 to battery B. Relay 76, upon attracting its armature 8 1, short circuits the condenser 96 through resistance 97, which operation is without particular effect at this time, however, the repeater E having been disconnected.

At the repeater M the relay 112, upon attracting its armature 127, completes a tin cuit for relay 113 as follows: ground at G, resistance 129, contact 128, armature 127, and winding of relay 113 to battery 13*. Relay 113, upon energizing, separates contact springs 137 and 138 whose function will be described later, and also by its other pair of contact springs completes a circuit for slow acting relay 117 as follows: ground at G, contact springs 159 and 160, contact springs 105 and 166, contact springs 158 and 157, contact springs 1 10 and 139, and winding of relay 117 to battery B.

In view of the large number of relays which 0 erate almost simultaneously it is thought kiest to continue with the energizing circuits of these relays before going into par ticulars concerning their functions separately. Relay 117, upon energizing, completes a circuit for relay 121 as follows: ground at G contact springs 142 and 143, and winding of relay 121 to battery 13. Re lay 1211, upon energizing, completes the following circuit for relay 123: ground at G, contact springs 150 and 151, and winding of relay 123 to battery 15. Relay 123, upon energizing, disconnects the normal ground connection of relay 12 1, closes its two upper pairs of 'contact springs (of no conse ucnce at this time), and completes a circuit for cut-01f rela 125 (Fig. 5) as follows: ground at G, win ing of relay 125, contact springs 175 and 176, and resistance 186 to battery B. The 'cut-ofi' relay 125, upon energizing, disconnects the line drop 126 in the usual man ner. A branch of the last described circuit extends to the sleeve of jack J 6 where by raising the potential of the sleeve above the normal ground potential the line is made busy to operators in the No. 2 exchange.

Returning now to relay 121, this relay, in addition to closing the circuit of relay 123-, also opens by its contact springs 152 and 153 a circuit for the upper windlng of relay 118 now closed by contact springs of relay 123; and by its contact springs 118 and 149 prepares a circuit for relay 11 1 which will be described later. The contact spring 151 of relay 121, now connected to ground at G, is seen to have several branch circuitsleading away from it, one of these circuits, that extending to relay 123, already having been mentioned. A second branch circuit extends b way of conductor 204 to the toll selector (Fig. 5) and will be again referred to. A third branch circuit may be made busy.

Returnin now to the relay 117 this re lay, in addition to closing the circuit of relay 121, removes at the same time ground from spring 141 and the conductor attached thereto. This is done to prevent possible interference by an operator at the No. 2 exchange. Should an operator disregard her busy test, plug into jack J 6 and operate key K she would operate relay 122, relay 124 being energized over the sleeve of her cord as will be described later, and thereby release the connection. Such an occurrence is prevented by the removal of ground from spring 141. Spring 143, from which a circuit already mentioned extends to relay 121, has also a branch circuit which may be traced by way of contact springs 130 and 131, conductor 203, and contact springs of relay 259 of the selector N (Fig. 5*) to the wiper 271 of the said selector, whence it will be traced further hereafter. A further result of the energization of relay 117 is the closure of a circuit for the line relay 250 of the toll selector N (Fig. 5) as follows: ground at G, winding 251 of relay 250, contact springs 248 and 249, conductor 202, contact springs 146 and 147, winding 110 of repeating coil R, contact springs 133 and 132, winding 109 of repeating coil R, contact springs 145 and 144 conductor 201, contact springs 246 and 24 and winding 252 of relay 250 to battery B Upon energizing, the line relay 250 completes a circuit from ground at G which extends by Way of the winding of slow acting relay 255 to battery B. Relay 255, upon attracting its armature, prepares circuits for the vertical and rotary magnets 256 and 257 in the well known manner.

The foregoing operations have all oc curred in response to the insertion of the plug in jack J 5 and the operation of the key K at the No. 1 exchange. The operator in charge of the call is now ready to operate the finger hole dial of the calling device S in accordance with the digit which corresponds to the level in the banks of the toll selectors assigned to toll lines extending to the No. 3 exchange. Since the required toll line is terminated in the second level (see Fig. 5) the proper digit to call is the digit 2.

In response to the manipulation of the dial the impulse springs 81 and 82 are separated twice momentarily thercby interrupting the circuit of the impulsing relays 76 and 112 a corresponding number of times. The resulting deiinergizations of relay 76 are of no effect, the automatic apparatus at the No. 1 exchange having been disconnected as hereinbefore described. Relay 112, however, at each deenergization breaks the circuit of relay 113 which relay instantly retracts its armature, thereby closing contact springs 137 and 138 and separating contact springs 139 and 140. Relay 117, being slow acting retains its armature attracted in spite of the interruptions of its circuit at contact springs 139 and 140. Now when relay 112 attracts its armature after each deenergization, it not only completes again the circuit of relay 113 but also, before relay 113 has had time to energize again, sends an impulse to relay1l4 over the following path: ground at G, resistance 129, contact 128, armature 127, contact springs 137 and 138, contact springs 148 and 149, contact springs 135 and 134, and winding 116 of relay 114 to battery B. Relay 114, in response to each impulse, attracts its armature and thereby separates contact springs 130 and 131, of no consequence at this time, and contact springs 132 and 133, which, it will be remembered, are included in the previously described circuit of the line relay 250 of the toll selector N.

Before continuing with the operation of the toll selector it will be well to consider more in detail the operation of relays 114, 113, and 112 in repeating the impulses. As the armature of relay 114 approaches the end of its stroke it separates contact springs 134 and 135, thereby breaking its own energizing circuit, and also closes at the same time contact springs 136 and 134, thereby short circuiting its winding 115. Induced currents in winding 115 serve to carry the armature a certain amount further in its stroke. The relay 113 pulls up fairly quick so that the relay 114 only receives a short impulse which is lengthened suitably by the effect of winding 115. It is evident that the length of time the contacts 132 and 133 are separated will be independent of the duration of the deenergization of relay 112, in fact, the combination of the relays 113 and 114 forms an impulse correcting device.

Referring now to Fig. 5, the line relay 250 of selector N in response to interruptions of its circuit at relay 114 of repeater M is deiinergized a number of times, sending an impulse at each deenergization from ground at G to the slow acting relay 258 and the vertical magnet 256 in series. The vertical magnet, in response to these impulses, steps up the shaft until the wipers stand opposite the level assigned to the toll lines extending to No. 3 exchange, or the second level. The relay 258, being slow acting retains its armature during the impulses and closes a circuit -lor the test relay 259, which relay locks itself to ground at G, off normal contact 263 having losed at the first vertical step, and also prepares at the same time a circuit for the rotary magnet 257. Since conductor 204 is already rounded at relay 121 of the repeater M it would be possible to omit the round G and upper springs of relay 255. ut in view of the fact that the rotary magnet 257 gets its operating ground from this conductor, it is considered advisable to round it directly in the selector at this time. At the end of the series of impulses the relay 258 deenergizes, thereby completing the circuit of the rotary magnet 257, whereupon the wipers of the selector are started rotating in search of an idle toll line terminating in the level to which they have been raised. As is well known, the rotary magnet inter rupts its own circuit and also the locking circuit of the test relay 259 at every energization, the contacts in the latter circuit, however, being short circuited by the test wiper 272 while passing over busy or grounded contacts. As soon, therefore, as the test wiper reaches an ungrounded test contact the test relay 259 deenergizes and opens the circuit of the rotary magnet, whereupon the wipers are brought to rest upon contacts which are terminals of an idle toll line extending to the No. 3 exchange. In the case under consideration, the first set of contacts of the second level is assumed to have been idle; therefore the wipers 270273, inclusive, are shown resting, respectively, on contacts 274277, inelusive. During the rotation of the wipers, in case rotation is necessary, the conductor 203, now grounded at relay 117 of the reeater M is disconnected from the wiper 271 by means of a pair of contact springs of the test relay 259. When the test relay 259 deenergizes, in addition to stopping the rotation of the wipers, this relay completes a circuit which may be traced as a branch of conductor 204 and which extends by way of interrupter contact 264, 011 normal contact 263, back contact of relay 259, and winding of line switching relay 253 to battery B The relay 253, upon energizing, disconnects the line conductors 201 and '202 from the windings of the line relay and connects them through to the wipers 270 and 27 3. The line relay 250 and slow acting relay now deenergize, the circuit of the release ma net 254 being held open by the line switc ing relay.

As a result of the foregoing operation of the toll selector, the trunk conductors 201, 202, 203, and 204 have been connected, respectively, with trunk conductors 208, 209, 210, and 211, which latter may be traced upward through Fig. 5 and to the right where they terminate in the repeater M (Fig. 6). By means of the associated repeating coil R the line conductors 208 and 209 are inductively connected with the toll line 305306.

It should be remembered at this point that conductors 203 and 204 are both grounded at repeater M (Fig. 4) and that these conductors are continued through to their respective wipers at the toll selector after its operation at practically the same instant, the former by the closure of the upper contacts of relay 259 and the latter by the closure of the interrupter contact 264. Bearing these facts in mind the operation of repeater M may be understood without diiiieulty. The first operation is that of the relay 311 whose energizing circuit may be traced as follows: ground at G (Fig. 4), contact springs 150 and 151, conductor 204, contact 264 (Fig. 5*), oil normal contact 263, wiper 272, bank contact 276, conductor 211, contact springs 361 and 362, and winding of relay 311 to battery 13*. Upon energizing, relay 311 removes the normal ground connection of relay 310 and completes an energizing circuit for cut-off relay 265 (Fig. 5) as follows: ground at G, winding of relay 365, contact springs 326 and 325, and resistance 324 to battery B. The cut-ofi' relay 365, upon attracting its armature, disconnects the drop 366 in the usual manner. A branch of the abov circuit extends to the sleeve of jack J where by raising the potential of the sleeve above the normal ground potential the toll line associated with ack J 7 is made busy to operators in the No. 2 exchange.

In addition to the foregoing, relay 311 forces its contact springs 331 and 329 into engagement, respectively, with contact springs 332 and 330, thereby completing simultaneously circuits for the upper and lower windings of relay 313. The circuit for the upper winding of relay 313 may be traced as a branch of the energizing circuit of relay 311 as follows: right hand terminal of relay 311, contact springs 349 and 348, contact springs 332 and 331, and winding 314 of relay 313 to battery B. The circuit for the lower winding of relay 313 may be traced over the following path: ground at G (Fig. 4), contact springs 142 and 143, contact springs 130 and 131, conductor 203, contact springs of relay 259 (Fig. 5'), wi e 271, bank contact 275, conductor 210, contact springs 329 and 330 (Fig. 6), contact springs 346 and 34-7, and Winding 315 of relay 313 to battery 13. Relay 313 is difi'erentially wound and since the energizin circuits of its two windings are comple ously it remains inoperative.

The apparatus is now in the proper condition to enable the operator at the No. 1 62- simultane change to signal the operator at the No. 3 exchange manually, as will be hereinafter described; but since in. the present case it is desired to connect automatically with a substation in the No. 3 exchange, certain further operations at the repeater M must be brought about in order to establish an impulsiug circuit over the toll line 305306 for operating the automatic switches in the No. 3 exchange.

These further changes at the repeater M are accomplished by the operator at the N0. 1 exchange who operates her dial at this juncture in accordance with the digit 1. As a result of the consequent interruption of its circuit, the imp-ulsing relay 112 of repeater M is deenergized momentarily and sends an impulse to relay 114. Relay 114, upon energizing, operates to separate momentarily the contact springs 130 and 131, thereby interrupting current flow in winding 315 of relay 313. The winding 314 at once becomes effective and relay 313 attracts its armature, thereby permanently opening the circuit of winding 315 at contact springs 346 and 347, and substituting therefor the winding of re lay 312 by closing contact springs 345 and 346. Before taking up the functions of relay 312, other results of the operation of relay 313 may be mentioned briefly as follows: By separating contact springs 343 and 344, a conductor later extended to relay 317 by the operation of relay 318 is opened; by the separation of contact springs 342 and 341, ground is disconnected from contact spring 335 of relay 312; and by the separation of contact springs 339 and.340 an extension of the grounded conductor 311 is disconnected from contact spring 334 of relay 312.

Returning now to relay 312, this relay, upon energizing, completes a circuit for the impulsing relays 319 and 414 (Fig. 7) as follows: ground at G, contact springs 432 and 433, winding of relay 414, Winding of retardation coil 413,windings 410 and 411 of repeating coil R in parallel, line conductors 305 and 306 in parallel, windings 370 and 371 of repeating coil R in parallel, winding of retardation coil 320, winding of relay 319, contact springs 337 and 338, contact springs 368 and 367 (Fig. 5), and resistance 369 to battery 13'. Relay 319, upon energizing, completes an energizing circuit for relay 318 from ground at G. The operation of relay 318, however, is of no importance.

At the No. 3 exchange relay 414, upon attracting its armature 415, short circuits the condenser 412, thereby completing a circuit for the line relays 440 and 441 of the repeater E (Fig 8) over the following path: ground at 1", winding of relay 440, conductor 436, contact springs 425 and 427, winding 418 of repeating coil R contact 416, armature 415, resistance 41.7, winding 419 of repeating coil R contact springs 430 and 428, conductor 4353, and Winding of relay 441 to battery B. Relay 441, upon energizing, closes a circuit for the slow acting relay 145 as follows: ground at G, contact springs 443 and 449, and winding of relay 445 to battery B. Relay 445 attracts its armature, and by means of contact springs 463, 464, and 465 shifts the normal connec tion of the sleeve of jack J from the wind ing of relay 420 (Fig. 7) to battery 15 by way of resistance 446. In this manner a guarding potential is placed on the sleeve of jack J and, furthermore, should an operator disregard her busy test or plug into jack J accidentally she will not release a connection already established automatically, for relay 420 has had its circuit opened as explained. Relay 445 also prepares, by means of contact springs 468 and 469, an energizing circuit for relay 444; and, by means of contact springs 466 and 467, a locking circuit for relay 442.

Relay 440, upon energizin closes a circuit for the line relay 512 of t e connector H Fig. 9) as follows: ground at G, Winding 513 of relay 51.2, contact springs 536 and 537 conductor 511, contact springs 451 and 450, contact springs 461 and 462, winding of retardation coil 443, contact springs 457 and 436, conductor 510, contact springs 538 and 535 and winding 514 of relay 512 to battery 13. Line relay 512 energizes over the foregoing circuit and thereby completes an energizing circuit from ground at (i for the slow acting relay 517 which relay in turn prepares a circuit for the Vertical magnet 513 in the well known manner. It may be mentioned here that in case selector switches are used the relay 517 will be provided with an extra pair of springs for supplying a holding ground to the selector or selectors.

The operator at the No. 1. exchange may now operate her calling device in accordance with the telephone number of the subscriber at substation A The digits already called, it will be understood, form no part of the telephone number as listed in the directory; but are special digits which must be prefixed to the regular telephone numbers by operators in distant exchanges who are calling subscribers in the No. 3 exchange via the No. 2 exchange.

The next operation of the calling device results as before in momentary deenergizations of the impulsing relay 112 (Fig. 4), which det nergizations affect relay 114 in a manner hereinbefo-re described. Relay 114, by means of contact springs 130 and 131, interrupts the circuit of relay 312 (Fig. 6) at each energization; relay 312, in response to these interruptions of its circuit, interrupts the circuit of impulsing relay 414 (Fig. 7 and relay 414, in turn, interrupts the circuit of line relays 440 and 441 of 

